Electro plumb bob



Jan. 12, 1954 E Q MlTCHELL 2,665,498

ELECTRO PLUMB BOB Filed June 24, 1950 INVEN TOR.

A TTOEWE Y Patented Jan. 12, 1954 UNITED STATES PATENT OFFICE.

ELEOTRO PLUMB 303 Edward C. Mitchell, San Diego, Calif. Application June24, 1950, Serial No. 170,126

Claims. (01. 33'.216)

My invention relates to electro plumb-bobs, and its objects are, toprovide a line plumbing device for readily determining, locating, illuminating and allowing the marking of the exact spot to be plumbed,particularly asused by mechanics for the accurate work required in theassembly of parts of airplanes or other sizable mechanicalconstructions, or as used by carpenters and others in the buildingtrades; to secure such illumination and to determine such locationthrough a plumb-bob provided with a centrally apertured tip or plummetadapted accurately to direct a beam of light upon the point so to beetermlned; to employ a novel arrangement of v a magnifying lens bulb,reflector, and dry batteries installed within the barrel of the bob inproducing said beam of light and in effecting said illum'nation; toallow the ready installation and removal of said bulb, reflector andbatteries within and from the said bob; to provide an improved switchfor manually turning on and off the light of the bob; to render theparts accessible for inspection, adjustment, removal, replacement andrepair; and in general to provide an electric plumb-bob which is simpleand economical of construction, saving of labor, efficient in action andof prolonged life and durability. These and other objects will appearfrom the drawing and as hereinafter set forth.

My invention generally consists in constructing a IJlUJIlb-bOb in theform of a cylindrical casing, the lower end or tip of which closedexcept for a centrally located narrow straight passageway of uniformdiameter extending downwardly therefrom; and within the main body ofwhich casing is formed an elongated chamber, whose walls are shaped tolocate and seat an electric lamp positioned to cast concentrated rays oflight downwardly through and out of said passageway, a contact reflectorwasher cooperating with said bulb in the intensified gathering and.casting of said rays, and a dry cell battery electrically connected withsaid bulb for energizing the same; the wall of said chamber adjacent tothe top of said plumb-bob being in threaded engagement with a thumbscrewplug serving as a switch for turning on or off the light of said bulbthrough suitable electrical connections made therewith and therefor.

My invention. further consists in other novel features of construction,and combinations and arrangements of parts illustrated in the drawing,and hereinafter more specifically described and claimed.

Attention is hereby directed to the accompanying drawing, illustrating apreferred form of my invention, in which similar numerals of designationrefer to similar parts throughout the several views, and in which-Figure 1 is an upright side elevational view of a plumb-bobembodying'said form of my invention, and

Fig. 2 is a longitudinal section thereof, turned on itsside and showingthe magnifying lens bulb, contact reflector washer, battery, andthumbscrew cap and associated parts in their respective relativepositions inside of the plumb-bob.

Referring to the drawing, the plumb-bob there shown generally comprises,the upright barrel or elongated rounded casing 8, having integraltherewith the perforated conical lower end 4; and the manuallyadjustable closure plug cap 5 threaded to engage with the upper end ofsaid barrel, both said casing and cap being of electric conductingmaterial. Within the bore of said barrel and extending nearly the lengththereof is the chamber 1; and within said chamber and in slidinengagement with the wall. thereof is the dry battery 8 of conventionalform and whose ends are supplied with the usual electric contacts. Atthe lower end of said chamber I, the wall thereof is constricted to formthe tapered shoulder 9, the rounded vestibule Ill, and the narrowstraight aperture I I of uniform diameter or cross section throughoutopening downwardly therefrom. All of these inside parts and openings areaxially aligned with the barrel of the plumb-bob.

Seated upon the shoulder 9, with its bulb I2 downwardly extending toenter and to eifect close engagement with the Wall of the vestibule i8,is the electric lamp iii, the threaded shank I4 of which extendsupwardly, and the electric contact I5 of which is centrally positionedto engage with the lower contact it; of the battery 8. Preferably thelower end of said bulb I2 is provided with the magnifying lens It, andsecured immediately above said bulb to the body of the lamp I3 andresting upon the shoulder E, is the washer I8 of electric conductingmaterial, the lower face of which is silvered or processed to reflectdownwardly such rays of the lamp I3 as are projected upwardly therefrom,and the rim of which is in sliding engagement with the wall of thechamber 1, and adapted to make electric contact therewith.

As illustrated in the drawing, the magnifying lens bulb I3, reflectorwasher, the parts for seating said lamp, and the small apertureaforesaid are centered and co-ordinated so as to gather and concentratethe rays of light coming from the bulb so as to cast downwardly a beamof light through said aperture and to produce upon the surface of theobject beneath a spot of light of minute size, serving as a convenientmeans of locating the exact plumbing point desired to be determinedthrough the use of the bob.

As shown, the plug cap 5 is provided with the central aperture I9extending therethrough, which aperture communicates with the socket 20formed in the bottom portion of such plug, and

' within which socket is lodged the knotted end of the plumb-line 2idriven outwardly through the aperture it, which line serves to suspendtherefrom the plumb-bob as a whole. For the purpose of engaging theupper electric contact of the battery 8, I preferably taper the bottomportion of the plug 5 outside of the wall of said socket so as to form anose, the end of which being forced downwardly upon rotation of the plugwill effect said engagement. In order, however, that the said plug andbattery may normally be out of engagement, when the plumb-bob is not inuse, I prefer to interpose therebetween the washer 22 of sponge rubberor rubberlike material serving as insulation between the two; but theopening of such washer being sufiiciently wide as to permit nose to beimpressed and thrust therethrough and to engage the said upper contactof the battery and thereby to turn on the light and to act as a switchin the way well understood in the art.

In order that the plumb-bob above described may be effective for all thepurposes above set forth, all parts of the bob and all the openingstherein must be in accurate axial alignment with the axis thereof, andbalanced distribution of the weight of such parts about a common centermust be accomplished, so that the bob may be undeviatingly accuratelysuspended above the spot to be plumbed. Also it is important that thepassageway of the narrow aperture It should be uniform in cross sectionthroughout, and preferably circular in form, in order that theconcentrated rays projected downwardly from the bulb l2 and intensifiedby the magnifying lens I! thereof, and reflective surface of the washeri8, may produce eifectively the small distinctive light spot which it isthe main object of the invention to secure.

To operate the device, for example, the light is first turned on throughmanipulation by the workman of the switch plug 5, and the bob is ofelectric conducting material threaded to engage with the top of saidcasing and positioned resiliently to make contact with the upper contactof said battery and to serve as a switch for opening and closing thecircuit thereof through said lamp; the said cap having a centralaperture extending therethrough and merging into a socket adapted toreceive the knotted end of the plumb line, and to lodge the sametherein.

2. An electric plumb-bob, comprising an upright symmetrically formedcasing of electric conducting material closed at the bottom except for anarrow aperture extending downwardly from the hollow of said casing; anelectric lamp seated within said casing and positioned to castdownwardly a beam of light through said aperture to form a pin pointilluminated spot upon the surface below; a dry cell battery locatedwithin said casing and adapted to be electrically connected to energizesaid lamp; a plug cap of electric conducting material tapered at thebottom to form a downwardly projecting nose and threaded to engage withthe inside of the top of said casing; a washer of insulating rubber-likematerial having its opening smaller than the end of said nose andnormally interposed within said casing between the upper contact of thebattery and said projecting nose, and allowing the end of such nose tobe extruded through the opening in said washer and to engage saidcontact upon the turning down of said cap on said washer and thereuponsuspended from a bulkhead, a stringer,

or other object directly above the point whose plumbed location it isdesired to determine, whereupon the said point being so located by thebeam of light being thrown thereon, such location is carefully markedand the work predicated thereon allowed to proceed accordingly withgreat saving of labor, time and computation.

My invention may be embodied in other specific forms without departingfrom the spirit or essential characteristics thereof. The presentembodiment, as above set forth is therefore to be considered in allrespects as illustrative and not restrictive, the scope of my inventionbeing indicated by the appended claims rather than by the foregoingdescription, and all changes which may come within the meaning and rangeof equivalency of the claims are therefore intended to be embracedtherein.

What I desire to secure by Letters Patent is:

1. An electric plumb-bob, comprising an upright symmetrically formedcurvilinear casing of electric conducting material with tip closed atthe bottom except for a narrow aperture of uniform diameter extendingdownwardly from the hollow of said casing; an electric lamp seatedwithin said casing and positioned to cast downwardly a beam of lightthrough said aperture to form a pin point illuminated spot upon thesurface below; a dry cell electric battery located within said casingand adapted to be electrically connected to energize said lamp; and acap plug compression thereof.

3; The subject matter of claim 2, the cap therein referred to having acentral aperture extending therethrough and merging into a socketadapted to receive the knotted end of the plumb line and to lodge thesame therein.

l. The subject matter of claim 2, including a disc light reflector ofelectric conducting material located within the casing above the lamp soas to reflect downwardly the rays of light coming upwardly therefrom andserving electrically as a contact to connect said lamp with said casing.

5. In an electric switch, the combination of a cylindrical casing havingan electric contact therein, a plug cap of electric conducting materialtapered at the bottom to form a downwardly projecting nose and threadedto engage with the inside of one end of said casing, a washer ofinsulating rubber-like material having an opening smaller than the endof said nose and normally interposed within said casing between saidcontact and said projecting nose, and allowing the end of said nose tobe extended through the opening in said washer and to engage saidcontact upon the turning down of said cap on said washer and compressionthereof.

EDWARD C. MITCHELL.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,364,893 Madigan Jan. 4, 1921 1,591,627 Hopkins July 6, 19262,225,405 Osterman Dec. 17, 1940 2,249,690 Gelardin July 15, 19412,467,608 Bischof Apr. 19, 1949 2,538,475 Skrastin Jan. 16, 19512,583,491 Orlando Jan. 22, 1952 FOREIGN PATENTS Number Country Date547,411 France 1922

